Burner with split combustion and exhaust induction air paths

ABSTRACT

A burner having a fuel tube, a heat recuperator disposed at least partially around the fuel tube, a cover disposed at least partially around the heat recuperator, and a housing coupled to the fuel tube. The housing has an air inlet, an exhaust outlet, and an eductor body. The eductor body has a first pathway for directing inlet air toward the heat recuperator and a second pathway directing inlet air into the exhaust outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional Patent Application No. 61/294,173, filed Jan. 12, 2010, which is incorporated by reference in its entirety herein.

BACKGROUND

Burners that withdraw combustion product gases from a furnace environment are known. Such burners typically incorporate an elongated hollow recuperator of ceramic material or the like that is disposed in spaced-apart surrounding relation to an axial gaseous fuel supply tube leading to a burner head. Dedicated combustion air travels along the annulus between the fuel supply tube and the recuperator for combustion with the gaseous fuel at the burner head. A portion of the combustion product gases then travels back over the exterior of the recuperator in counter-current flow to the combustion air. When the burner has an open- ended construction, the combustion product gases are typically drawn out of the furnace and into a low pressure venturi exhaust outlet at the rear of the burner. The venturi exhaust outlet is typically fed with a high velocity air jet to generate a low pressure zone which pulls the combustion product gases out of the furnace due to the pressure differential between the furnace interior and the venturi exhaust outlet. While such prior systems work well, the need for an air supply feeding the venturi exhaust outlet results in increased complexity.

BRIEF SUMMARY

The present invention relates generally to an open end burner adapted to withdraw combustion product gases from a furnace environment. More particularly, the invention relates to a burner incorporating a housing having a split air path such that a first portion of the intake air is directed along the burner to a combustion chamber and a second minority portion of the intake air is directed to an exhaust outlet in fluid communication with a combustion gas return sleeve. Directing a portion of the intake air to the exhaust outlet provides a low pressure zone at the exhaust outlet thereby drawing combustion product gases through the combustion gas return path and into the exhaust outlet.

The present invention provides advantages and alternatives over the prior art by incorporating a system in which the inlet air which is delivered by a blower or other pressure source is split such that a first portion is delivered to a combustion chamber while a second portion is delivered through an annular constriction and into an exhaust outlet in fluid communication with the combustion product gas return path. The inlet air passing through the annular constriction has sufficient velocity to generate a low pressure zone within the exhaust outlet thereby pulling the combustion product gases out of the furnace and into the exhaust outlet. A single air supply such as a blower or the like can thus be used for combustion air feed as well as for inducing recovery of combustion product gases. System complexity is thereby substantially reduced.

A burner is disclosed having a fuel tube, a heat recuperator disposed at least partially around the fuel tube, a cover disposed at least partially around the heat recuperator, and a housing coupled to the fuel tube. The housing has an air inlet, an exhaust outlet, and an eductor body. The eductor body has a first pathway for directing inlet air toward the heat recuperator and a second pathway directing inlet air into the exhaust outlet.

An eductor for a burner is disclosed. The eductor has an eductor body. The eductor body has an air inlet and an exhaust outlet. The eductor body has a bypass pathway for air from the air inlet to enter the exhaust outlet.

A method of operating a burner is disclosed. A burner is provided having a housing, a fuel tube coupled to the housing, a heat recuperator disposed at least partially around the fuel tube, and a cover disposed at least partially around the heat recuperator. The housing has an air inlet for receiving air into the housing and an exhaust outlet for exhausting air from the housing. A first portion of the air from the air inlet is directed into the heat recuperator, and a second portion of the air from the air inlet is directed into the exhaust outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an exemplary burner incorporating a housing having an exhaust outlet operatively connected to a split air feed system;

FIG. 2 is another perspective view of a burner with a housing having an exhaust outlet operatively connected to a split air feed system;

FIG. 3 is a cross-sectional view of the housing of FIG. 1 illustrating split air delivery and return paths;

FIG. 4 is a perspective view of the eductor body shown in FIG. 1;

FIG. 5 is a perspective cross-sectional view of the eductor body shown in FIG. 4;

FIG. 6 is a cross-sectional view of the eductor body shown in FIG. 4;

FIG. 7 is an enlarged fragmentary view of a portion of the eductor body shown in FIG. 6;

FIG. 8 is a fragmentary perspective view showing a threaded insert sleeve adapted for insertion into an exhaust outlet to provide an annular constriction opening to the interior of the exhaust outlet;

FIG. 9 is a perspective view of another embodiment of a burner incorporating a housing having an exhaust outlet operatively connected to a split air feed system;

FIG. 10 is a fragmentary cross-sectional view of the burner shown in FIG. 9;

FIG. 11 is a perspective view of the eductor body shown in FIG. 9;

FIG. 12 is a top plan view of the eductor body shown in FIG. 11; and

FIG. 13 is a cross-sectional view of the eductor body shown in FIG. 11 taken through line 13-13 of FIG. 12.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like elements are designated by like reference numbers in the various views. FIG. 1 illustrates a burner 10 including a generally hollow tubular cover tube 12 having an open end 14 that projects into a furnace or other environment to be heated. As best seen in FIG. 3, the cover tube 12 is disposed in surrounding relation to a hollow, substantially cylindrical heat recuperator 16 of ceramic or the like having a convoluted surface extending outwardly from a housing 18. The recuperator 16 surrounds a fuel tube 20 feeding a burner head within a combustion chamber located adjacent to the open end 14.

As shown in FIG. 3, an air supply designated generally as 24 is introduced into an air inlet port 26 from a blower 30 or other suitable supply source. Within the housing 18, the air supply 24 is split into a combustion feed stream 32 and an exhaust induction stream 34. An eductor body 54 is attached to the housing 18. The air inlet port 26 is formed in the eductor body 54, which provides an interior pathway 56 to the interior of the recuperator 16. In this regard, it is contemplated that a substantial majority of the air supply will be directed to the combustion feed stream 32.

In practice, the combustion feed stream 32 passes along an annular conduit between the fuel tube 20 and the inner surface of the recuperator 16 for delivery to the combustion chamber. At the combustion chamber, the combustion air reacts with fuel carried by the fuel tube 20 in an oxidation reaction to generate hot combustion gases which exit into a furnace through a nozzle 36 (shown in FIG. 1). At least a portion of the heated combustion product gases generated by the burner travel back to the housing 18 along a travel path between the outer surface of the recuperator 16 and the inner surface of the cover tube 12. Thus, the heated combustion product gases traveling to the housing 18 move in counter-current flow relative to the combustion feed stream 32 with the walls of the recuperator forming a divider between the two gas flow streams. As shown, the housing 18 includes an exhaust outlet 40 in fluid communication with the return path of the combustion product gases. The exhaust outlet 40 is provided by an opening in the eductor body 54. Thus, the combustion product gases 35 may exit through the exhaust outlet 40. An alternative eductor body shape is shown in FIG. 2, but it will be appreciated that the eductor body 54 can have any suitable shape and size.

Most furnaces are not pressurized systems. Thus, in order to induce the flow of combustion product gases from the furnace to the exhaust outlet 40, it is desirable to establish a low pressure zone at the exhaust outlet. This low pressure zone creates a pressure differential between the furnace and the exhaust outlet 40 thereby promoting the flow of combustion product gases from the furnace.

Referring to FIGS. 3-8, in an embodiment of the present invention, a low pressure zone is generated within the housing 18 by introduction of a threaded sleeve 50 at the exhaust outlet 40 that extends at least partially into the eductor body 54.

In certain embodiments, the eductor body 54 may include a stepped base 52 which is best seen in FIGS. 5-7. The stepped base 52 can contact the lower surface of the threaded sleeve 50 when the threaded sleeve is screwed in place. As can be seen, the stepped base 52 can be shaped such that it does not extend around the entire perimeter of the exhaust outlet. In particular, the stepped base may be shaped such that it does not extend along a segment in general alignment with the air inlet port 26. This discontinuity in the stepped base results in a minimum narrow width opening beneath the lower edge of the threaded sleeve 50 in substantial alignment with the air inlet port 26. Thus, the exhaust induction stream 34 may pass through the opening 60 and into the interior of the exhaust outlet 40. Of course, it will be appreciated that the size of the opening 60 between the inlet air and the exhaust air can be controlled by how far the threaded sleeve 50 is rotated into the eductor body 54. For example, the size of the opening 60 is larger when the threaded sleeve 50 extends only partially into the eductor body 54 than when the threaded sleeve 50 extends fully into the eductor body 54. It will be appreciated that the threaded sleeve can have any suitable shape and size. It will further be appreciated that the structure providing a portion of the inlet air stream (i.e., the exhaust induction stream 34) into the exhaust air stream can be any suitable structure of any suitable shape and size.

As will be appreciated, due to the narrow width of the opening 60 beneath the lower edge of the threaded sleeve 50, the exhaust induction stream 34 entering the exhaust outlet 40 may obtain a substantial velocity. This enhanced velocity results in a corresponding pressure reduction within the exhaust outlet 40 thereby inducing flow from the furnace to the exhaust outlet. Accordingly, a controlled outlet is provided for combustion product gases generated by the burner. Moreover, heat from the combustion product gases passing over the recuperator 16 may be used to pre-heat the combustion air feed stream which further improves the efficiency of the burner.

Referring now to FIGS. 9 and 10, another embodiment of a burner 100 is shown. The burner 100 can include a tube cover 112 with an open end 114. The burner can include a housing 118 having an eductor body 154 attached thereto. The eductor body 154 can provide an air inlet port 126 for providing air to the burner. As shown, for example, the air inlet port 126 is disposed on the side of the eductor body 154 instead of the end of the eductor body 154 as shown in FIG. 1. It will be appreciated that the air inlet port 126 may be disposed in any suitable position on the eductor body 154. The eductor body 154 may also provide an exhaust outlet 140 for combustion gases to exit the burner. The exhaust outlet 140 may be threaded to permit the insertion and attachment of a threaded sleeve 150. The threaded sleeve 150 can provide a conduit to direct combustion gases away from the burner 100.

An air supply is introduced into an air inlet port 126 from a blower or other suitable supply source. Within the housing 118, the air supply 124 is split into a combustion feed stream 132 and an exhaust induction stream 134. The eductor body 154 provides an interior pathway 156 to the interior of the recuperator 116. In this regard, it is contemplated that a substantial majority of the air supply will be directed to the combustion feed stream 132.

In practice, the combustion feed stream 132 may pass along an annular conduit between the fuel tube 120 and the inner surface of the recuperator 116 for delivery to the combustion chamber. At the combustion chamber, the combustion air reacts with fuel carried by the fuel tube 120 in an oxidation reaction to generate hot combustion gases which exit into a furnace through a nozzle (such as the nozzle 36 shown in FIG. 1). At least a portion of the heated combustion product gases generated by the burner travel back to the housing 118 along a travel path between the outer surface of the recuperator 116 and the inner surface of the cover tube 112. Thus, the heated combustion product gases traveling to the housing 118 move in counter-current flow relative to the combustion feed stream 132 with the walls of the recuperator 116 forming a divider between the two gas flow streams. As shown, the housing 118 includes an exhaust outlet 140 in fluid communication with the return path of the combustion product gases. The exhaust outlet 140 is provided by an opening in the eductor body 154. Thus, the combustion product gases 135 may exit through the exhaust outlet 140.

As discussed above, most furnaces are not pressurized systems. Thus, in order to induce the flow of combustion product gases from the furnace to the exhaust outlet 140 it is desirable to establish a low pressure zone at the exhaust outlet 140. This low pressure zone creates a pressure differential between the furnace and the exhaust outlet 140 thereby promoting the flow of combustion product gases from the furnace.

Referring to FIGS. 10-13, in an embodiment of the present invention, a low pressure zone is generated within the housing 118 by introduction of a threaded sleeve 150 at the exhaust outlet 140 extending into the eductor body 154. The threaded sleeve 150 can be inserted any desired distance into the eductor body 154. When the threaded sleeve 150 is not fully inserted into the eductor body 154, an opening 160 exists between the lower end of the threaded sleeve 150 and an interior wall of the eductor body 154. This opening 160 is exposed to the input air stream, and thus a certain amount of the input air may be directed toward the opening 160 to form an exhaust induction stream 134. Thus, the exhaust induction stream 134 may pass through the opening 160 and into the interior of the exhaust outlet 140. Of course, it will be appreciated that the size of the opening 160 between the inlet air and the exhaust air can be controlled by how far the threaded sleeve 150 is rotated into the eductor body 154. For example, the size of the opening 160 is larger when the threaded sleeve 150 only partially extends into the eductor body 154 than when the threaded sleeve 150 fully or nearly fully extends into the eductor body 154. It will also be appreciated that the velocity of the exhaust induction stream 134 may increase as the opening 160 is made smaller, and the velocity of the exhaust induction stream 134 may decrease as the opening 160 is made larger. The opening 160 may be provided around the circumference of the lower end of the threaded sleeve 150 as shown in FIG. 10. It will be appreciated that the threaded sleeve can have any suitable shape and size. It will further be appreciated that the structure providing a portion of the inlet air stream (i.e., the exhaust induction stream 134) into the exhaust air stream can be any suitable structure of any suitable shape and size.

As will be appreciated, due to the opening 160 beneath the lower edge of the threaded sleeve 150, the exhaust induction stream 134 entering the exhaust outlet 140 may obtain a substantial velocity. This enhanced velocity may result in a corresponding pressure reduction within the exhaust outlet 140 thereby inducing flow from the furnace to the exhaust outlet 140. Accordingly, a controlled outlet is provided for combustion product gases generated by the burner 100. Moreover, heat from the combustion product gases passing over the recuperator 116 may be used to pre-heat the combustion air feed stream which further improves the efficiency of the burner 100.

As noted, the amount of air forming the exhaust induction stream 134 can be controlled by the size of the opening 160 formed when inserting the threaded sleeve 150 into the eductor body 154. Further structures may be provided that can be used to adjust the exhaust induction stream 134. For example, as shown in FIGS. 11-13, an adjustable device may be provided for adjusting the exhaust induction stream after the sleeve 150 has been inserted into the eductor body 154. The adjustable device may be in the form of a damper 168 having a damper plate 170, a damper shaft 172, and a damper indicator 174. The damper plate 170 can be disposed inside the eductor body 154 between the air inlet port 126 and the opening 160. The damper shaft 172 is connected to the damper plate 170 inside the eductor body 154, and also extends outside the eductor body 154 where it is connected to the damper indicator 174. The damper shaft 172 can be rotatable to move the damper plate 170 between positions where it partially or completely restricts the flow of air to the opening 160 and positions where it does not restrict the flow of air to the opening 160. The damper indicator 174 is externally disposed and informs a user as to the position of the damper plate 170. The damper indicator 174 can also provide a handhold to assist with moving the damper plate 170. Thus, the damper 168 may permit a user to adjust the amount of air passing through the opening 160 and adjust the air velocity without adjusting the threaded sleeve 150.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

1. A burner comprising: a fuel tube; a heat recuperator disposed at least partially around the fuel tube; a cover disposed at least partially around the heat recuperator; and a housing coupled to the fuel tube, the housing having an air inlet and an exhaust outlet, the housing having an eductor body, the eductor body having a first pathway for directing inlet air toward the heat recuperator, and the eductor body having a second pathway directing inlet air into the exhaust outlet.
 2. The burner of claim 1 wherein the air inlet and the exhaust outlet are part of the eductor body.
 3. The burner of claim 1 wherein the air from the second pathway is directed into the exhaust outlet via an opening into the exhaust outlet.
 4. The burner of claim 3 further comprising a sleeve disposed at least partially in the eductor body, wherein the opening is formed between the sleeve and an interior surface of the eductor body.
 5. The burner of claim 4 wherein the eductor body has a stepped base for contacting the sleeve.
 6. The burner of claim 4 wherein the sleeve is adjustable to determine a size of the opening.
 7. The burner of claim 1 further comprising a damper for restricting air passage along the second pathway.
 8. The burner of claim 7 wherein the damper is adjustable from an exterior of the housing.
 9. The burner of claim 1 wherein the exhaust outlet receives a combustion gas, and the inlet air directed along the second pathway is combined with the combustion gas, the inlet air directed along the second pathway having not undergone combustion.
 10. The burner of claim 1 wherein a majority of the total inlet air is directed along the first pathway.
 11. An eductor for a burner comprising: an eductor body, the eductor body having an air inlet and an exhaust outlet; the eductor body having a bypass pathway for air from the air inlet to enter the exhaust outlet.
 12. The eductor of claim 1 wherein the air from the bypass pathway is directed into the exhaust outlet via an opening into the exhaust outlet.
 13. The eductor of claim 12 further comprising a sleeve disposed at least partially in the eductor body, wherein the opening is formed between the sleeve and an interior surface of the eductor body.
 14. The eductor of claim 13 wherein the eductor body has a stepped base for contacting the sleeve.
 15. The eductor of claim 13 wherein the sleeve is adjustable to determine a size of the opening.
 16. The eductor of claim 11 further comprising a damper for restricting air passage along the bypass pathway.
 17. The eductor of claim 16 wherein the damper is adjustable from an exterior of the eductor.
 18. The eductor of claim 11 wherein the exhaust outlet receives a combustion gas, and the inlet air directed along the bypass pathway is combined with the combustion gas, the inlet air directed along the bypass pathway having not undergone combustion.
 19. The burner of claim 1 wherein a minority of the total inlet air is directed along the bypass pathway.
 20. A method of operating a burner comprising: providing a burner having a housing, a fuel tube coupled to the housing, a heat recuperator disposed at least partially around the fuel tube, and a cover disposed at least partially around the heat recuperator, the housing having an air inlet for receiving air into the housing and an exhaust outlet for exhausting combustion gases from the housing; directing a first portion of the air from the air inlet into the heat recuperator; and directing a second portion of the air from the air inlet into the exhaust outlet. 